Understanding the simultaneous biodegradation of thiocyanate and salicylic acid by Paracoccus thiocyanatus and Pseudomonas putida

Abstract

Phenolic and cyanide compounds, which frequently appear mixed in several industrial effluents, are difficult to be biodegraded under certain conditions. In this work, salicylic acid (SA) and thiocyanate (SCN−) were selected as model pollutants of these two families and experiments of biodegradation with specific microorganisms were developed. It was found that the best well-known bacteria able to biodegrade each one of these pollutants, Pseudomonas putida for SA and Paracoccus thiocyanatus for SCN−, do not biodegrade the other one. Therefore, the co-culture was required, producing interesting interaction phenomena. When both pollutants were simultaneously biodegraded, a commensalism effect was observed improving SCN− removal. Experimental data for SCN− and SA removals were successfully fitted to zero reaction kinetic orders, with induction time in the case of SCN−, and substrate dependences were fitted to Tessier models. A flow cytometry method was developed and employed to obtain the evolution of the viable, damaged and dead cells for different substrate concentration and the degree of agglomeration in the co-culture experiments.